The invention relates generally to integrated circuit package solder pad designs.
Reliability of handheld devices and other devices relating to drop performance or shock performance is increasingly important. For example, when a cell phone or other handheld device is accidentally dropped by a user, integrated circuits including integrated circuit packages within the cell phone can be subjected to high stresses for short durations. In some cases, the stress is sufficiently high to cause solder joints of packages or integrated circuit components to break from their substrates. A common failure mode is a cracking through an intermetallic (IMC) layer on a solder pad at a substrate surface through, for example, a ball grid array type solder joint based connection. As is known, the intermetallic layer is produced during a solder reflow process. The IMC can be brittle.
Common designs of solder pads have been flat with no features. As such, it is easy for a crack to propagate along the (IMC) layer between the solder ball and solder pad surface. Such cracks may only require a relatively small energy to propagate through the solder joint.
Proposed solutions that attempt to reduce the solder joint cracking problem, include using different solder alloys for flat solder pads. For example, the reduction of nickel has been employed on flat surfaces when using a tin based solder alloy. However, undesirable cracking of the solder joint is still apparent with such solutions.
As such, there is a need for an improved integrated circuit solder joint technology.